1. Field of the Invention
The present invention relates to an image formation apparatus and a network system containing image formation apparatuses, and, in particular, to an image formation apparatus having a function such that, when a power supply to the image formation apparatus is shut down by an external operation, predetermined information is saved, and, thus, an occurrence of problem due to the event of power supply shut down can be avoided.
2. Description of the Related Art
In an image formation apparatus, such as a copier, a printer or a composite machine which has both of these functions, upon a turning-off operation performed on a power supply switch, the power supply to this machine is cut off completely, and, thus, a power supply to each control part thereof is stopped. That is, when an unexpected power supply turning-off operation by a user occurs, the control function in the machine naturally dies without no recognition thereof is made by a control management part (CPU etc.) of the machine itself. When such a situation occurs in the image formation apparatus which operates under a communications network environment, communications with this image formation apparatus which is acting a terminal of the network are suddenly interrupted. Thereby, this event is regarded as occurring due to a communications failure or a machine trouble.
For example, when a power switch is turned off by an operation of a user during a printing operation is on the way in the image formation apparatus, all the operations of a drive system and a control system stop. In this case, some problem may occur in that, for example, a transfer paper on which a printing operation is being made is left inside of the machine enclosure, a large amount of image data which is currently produced during an image formation preparation process is lost, or the like. Especially, a user normally operates a machine by a remote control manner at a position distant from the machine itself, and, usually, after estimating that a printing operation has been completed, the user goes there to take a printed matter, under a communications network environment. In such a situation, a problem may occur in that, when a power supply to the machine has been shut off by an operation of another user as mentioned above, the above-mentioned printed matter may not have been actually completed without no proper notification of this situation being given due to the sudden power failure in the machine which does not allow the machine to perform such a notification operation.
Further, when such an abnormal interruption in operation of a machine caused by an event of power supply being turned off, and thus, a communications failure in the network occur, since the control operation is interrupted without recognition thereof by the control management unit (CPU or so) of the machine itself, a considerable time may be needed for analyzing this event for the cause thereof, and, thus, a considerable time is needed until the system recovers from this situation.
In order to solve such a problem, a system is demanded in which information indicating that the power switch has been manually turned off is stored as history information. For example, Japanese laid-open patent application No. 2000-172348 discloses a system in which a control power switch is provided other than a main power switch. Thereby, without providing any other special device, power saving can be achieved on an occasion in which the machine is not actually used.
According to this prior art, the control power switch does not directly cut off a power supply from a main commercial power source, and a signal concerning an operation of the switch is monitored. Then, at a time of a turning off operation made by a user is detected; the actual power supply is cut off by means of a predetermined power supply cut off circuit. In this prior art, after detecting the turning off operation of the control power switch, some control processing which is needed with respect to a power shut down event is performed automatically, and turning off of actual power supply is performed after that.
With such a configuration, since an actual power supply shut down event can be recognized beforehand by a control management unit as mentioned above, an abnormal or problematic interruption of the machine can be avoided, and a fact that the operation interruption of the machine has occurred due to a manual turning-off operation performed by a user can be properly notified to the outside through a communications network. Accordingly, a work of analyzing this event for a cause thereof should not be performed
However, in this prior art, some problem may occur as will be now discussed. That is, on an occasion of CPU's run-away or an endless heating operation of a fixing heater due to malfunction, although a user thus may wish to shut down the machine immediately, an emergency shut down may not be properly achieved due to the above-mentioned lengthy operation to be performed before an actual power shut down operation.